1. Field of the Invention
Embodiments of the present invention relate to a drive transmission device including drive transmission members that transmit drive from a drive source to a driven object, and all or a part of which forms a gear train, and to a drive device and an image forming apparatus including the drive transmission device.
2. Description of the Related Art
A background image forming apparatus is known that includes a plurality of image forming units that form toner images of a plurality of colors including black on image carrying members corresponding to the respective colors.
In this type of image forming apparatus, the toner images formed on the image carrying members corresponding to the respective colors are superimposed on one another on a recording medium to form a full-color image on the recording medium. To attain highly accurate color registration on the recording medium, therefore, it is desired to reduce superimposition deviation of the colors caused by, for example, variations in rotation cycle among the image carrying members. To match the rotational phases of the image carrying members corresponding to the respective colors and thereby reducing the superimposition deviation of the colors, the rotational positions of the image carrying members for the respective colors are detected, and the driving of drive sources for driving to rotate the image carrying members is controlled on the basis of the results of detection, thereby matching the phases of the respective colors.
As a configuration for detecting the rotational position of each of the image carrying members for the respective colors, a configuration has been proposed in which a position detection member for detecting the rotational position is provided to an image carrying member drive gear that is coaxially fixed to the image carrying member and receives rotational drive transmitted from the drive source, and which detects the position detection member by using a detection unit provided to the image forming apparatus.
In a drive transmission device including the image carrying member drive gear to transmit the rotational drive from the drive source to the image carrying member, however, the image carrying member drive gear is charged to a relatively high potential in some cases. This is because the image carrying member drive gear is frictionally charged by sliding friction occurring between the image carrying member drive gear and a drive transmission gear that meshes with the image carrying member drive gear to transmit the drive thereto. If the image carrying member drive gear is charged to a relatively high potential, dielectric breakdown may occur between the image carrying member drive gear and the detection unit disposed in the vicinity thereof and cause abnormal output from the detection unit. As a configuration for reducing the occurrence of dielectric breakdown, it is conceivable to provide a conductive member around the detection unit. However, if there is a large error in the installation position of the conductive member relative to the installation position of the detection unit disposed in the vicinity of the image carrying member drive gear, the conductive member may come into contact with and damage the image carrying member drive gear.
The above-described issue is not limited to the drive transmission device in which the image carrying member drive gear serves as the detection target gear, the rotational position of which is detected by the detection unit. The issue may also arise in a configuration that uses the detection unit to detect the rotational position of at least one of the gears forming a gear train.